A strategy for suppressing the torque ripple in three-phase four-switch inverter-fed PMSM drives

This paper proposes a strategy to suppress the torque ripple based on three-phase four-switch (TPFS) inverter for the permanent magnet synchronous motor (PMSM) drives system to ensure safe and reliable operation in case of single-phase open circuit of the three-phase six-switch (TPSS) inverter. When a TPFS inverter fault-tolerant topology is adopted, the voltage fluctuations of the DC-split capacitors will cause the command voltages and currents to have a second harmonic components in addition to the effective DC components. This also results in the existence of second harmonics in the torque and speed, which causes the torque and speed to generate periodic ripple. Therefore, in order to solve this problem, this paper proposes a proportional-integral quasi-resonant (PIQR) control strategy for the current loop. By suppressing the second harmonics in the motor currents, the current waveform can be improved, and the ripple in the torque and speed can be well suppressed. The feasibility and effectiveness of the strategy are verified by simulation results.